Sheet Metal Tie-Rods for Multi-Stage Centrifugal Pump Assembly
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Solution Overview
Problem
Multistage centrifugal pumps face difficulties in assembly and design due to the complexity and expense of traditional tie-rods, which are heavy, prone to deformation, and require significant forces to accommodate motor and thermal expansion loads.
Innovation Solution
The use of sheet metal tie-rods, which are formed in sections and welded with a short threaded part, allowing for easier assembly, reduced moment loads, and improved aesthetics by being flush with the pump body, with projections for secure fixation and thermal connection to the annular channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional round tie-rods are used, then mechanical retention and force accommodation are achieved, but assembly difficulty, weight, and cost increase
Solution Approach 1:
The tie-rod is divided into a sheet metal body and a separate threaded end piece that is welded to it. This segmentation allows the main body to be easily formed from sheet metal while the threaded end provides the necessary fastening capability, simplifying assembly compared to traditional fully-threaded round rods.
Solution Approach 2:
The tie-rod transitions from a traditional round cross-section to a sheet metal construction with a specific profile. This parameter change in geometry and material form enables easier assembly and reduced weight while maintaining the necessary mechanical retention through the combination of sheet metal strength and welded threaded end.
2Force
If traditional round tie-rods are used, then force accommodation is achieved, but weight and material cost increase
Solution Approach 1:
The tie-rod changes from a solid round rod to a sheet metal construction with optimized cross-section. This parameter change reduces material usage and weight while the welded threaded end ensures adequate force accommodation through proper material selection and joint design.
Solution Approach 2:
The tie-rod combines sheet metal with a threaded end piece through welding, creating a composite structure that optimizes both weight and strength. The sheet metal provides lightweight structural integrity while the threaded end provides secure fastening capability.
3Strength
If traditional round tie-rods are used, then mechanical retention is achieved, but bending moments and deformation risk increase
Solution Approach 1:
The tie-rod geometry changes from a round cross-section to a sheet metal profile that can be optimized for reduced bending moments. The sheet metal construction allows for design adjustments that minimize lateral projection and reduce leverage effects that cause bending moments and deformation.
4Force
If traditional round tie-rods are used, then force accommodation is achieved, but thermal stress accommodation is problematic
Solution Approach 1:
The sheet metal construction with its different thermal properties compared to traditional round rod material provides improved thermal stress accommodation. The sheet metal can be designed with appropriate thickness and profile to handle thermal expansion and contraction forces more effectively.
5Ease of manufacture
If sheet metal tie-rods are used, then assembly ease and cost reduction are achieved, but manufacturing precision requirements increase
Solution Approach 1:
The tie-rod is segmented into a sheet metal body and a threaded end piece. The sheet metal body can be easily formed and assembled, while the pre-fabricated threaded end piece provides precise threading. The welding joint between the two segments requires precision, but this is localized to a specific area rather than the entire component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sheet metal tie-rods simplify assembly, reduce material costs, enhance structural stability, and minimize thermal stresses, while providing a more aesthetically pleasing design and efficient force transmission.
Implementation Method 1
The sheet metal tie-rods are formed in sections and welded with a short threaded part
Data Source
AI summary
A multistage centrifugal pump has a foot part (2) and a head part (9), between which pump stages are integrated. The head part (9) and the foot part (2) are connected via tie-rods (11) which with one end are fastened on the head part (9) and with the other end are fastened on the foot part (2). The tie-rods (11) at one end comprise a thread (14), with which they are tightened on the head part (9). The tie-rods (11) are formed from sheet metal. At the end opposite the thread, the tie-rods include a recess, with which recess the tie-rods are each positively fixed on the foot part (2), at least in the tensile direction (22).